1. Field of the Invention
The present invention relates to a deflection compensating device for a converging lens and more particularly, to a charged particle beam exposing device and an electrostatic deflecting apparatus.
2. Description of the Related Art
Deflection is a basic technique used in a charged particle beam method. Namely, in an exposure method using an electron beam, a low aberration high speed deflection is required, and accordingly, the deflectors are separated into those giving a large deflection and those giving a small deflection. An electromagnetic type deflector is used for the large deflection, and an electrostatic multi-electrode cylindrical type deflector operated at a high scanning speed and a low voltage is used for the small deflection. As a deflecting system by which a deflection aberration due to a magnetic field is lessened, a Moving Objective Lens (MOL) system is well known. In the MOL system, for the large deflection a lens center is moved by a transversely directed magnetic field so that a deflected beam passes through a center of a magnetic field type conversing lens. Similarly, in the electrical field type deflector for a small deflection, to keep the deflection aberrations at a low level, the lens center can be moved in accordance with an amount of deflection, to reduce the aberration. Note, since the electrical field type deflection speed is higher than the magnetic field type deflection speed, the movement of the lens center in accordance with the electrical field type deflection speed cannot be obtained by a transversely directed magnetic field.
Further, each electrical field type deflector has a high degree of accuracy of divided angles for electrodes and of the assembly. Nevertheless, when the electrical field type deflectors are formed with a structure having a plurality of stages, a high concentricity of each deflector with respect to the lens axis, mutual concentricities between deflectors, and a high degree of accuracy of relative angles and positions is not easily obtained, due to the method of fixing to a column at which the deflectors are supported.
Further, as shown in FIG. 1, a converging lens 8 and a last converging lens 9 are provided around a vacuum wall 10, and since an electrical field type deflector 11 for a small deflection is provided near the last converging lens 9, it should be provided inside a coil which is a magnetic field type deflector 13 for a large deflection. Further, a hermetic seal 12 and a vacuum flange 14 should be provided inside the coil 13. Therefore, the provision of a plurality of electrical field type deflectors 11 near the last converging lens 9 increases the size of the last lens stage structure of the column, with the result that the deflection aberration becomes larger.
Therefore, when a plurality of electrical type deflectors are assembled as a structure having a plurality of stages, the last lens must have a long length, with the result that a low deflection aberration can not be realized. Even if the positioning of above mentioned structure can be carried out, if the assembly is once decomposed this complex and difficult positioning must be again carried out.